Hi Tim.

This is how I figure it out.

Once I have configured the FMC up to the point that it says that the flight plan and the aircraft configuration is "complete" (on the bottom right hand side of the CDU display on the Takeoff Ref page).
I click on the VNAV button and go to Page 2/3 (LIM CRZ REF page) and on the two lines that  display STEP SIZE, OPT, MAX I select the next altitude odd or even depending on route heading according to the MEAs (Eastbound (0-179 deg) fly ODD and Westbound (180-359 deg) fly EVEN).

E.G. VNAV page 2/3 displays OPT as FL304 and I'm heading Eastbound, then I set my initial cruise altitude at FL310.

I usually go for a 2000 STEP CLIMB because I'm not yet familiar with the full MEAs and I'm too darned lazy to do so and I just want to go and fly.  :o

I hope this helps.

If you are still confused. Say so and I will take some time to use pictures to display how I do it.

Mark

Note: To get more detailed information on MEAs go to http://vatsim.net/prc/ . Select VATSIM 200/300 Prereqs  (on the left of screen). In the next window that opens select  216 - How High to Fly - MEAs (MEAs and altitude selection) - HowHightoFly by EricStearns. Click on the HowToFly and look under the heading Direction of Flight.